Romney has said he pays taxes every year and that Senate Majority Leader Harry Reid, D-Nev., is wrong.

Top Republicans say Reid is telling lies.

Pelosi, who was campaigning in Florida, said though the allegation is unproven she didn't think Reid was wrong to put it out there. Reid has said only that the tip came from a former Romney associate. He also has said he isn't sure it's true.

Reid has raised the claim in media interviews and on the Senate floor.

Pelosi said she believes Reid when he says he got the information from a credible source. She also said it's up to Romney to release more of his income tax returns to prove that Reid is wrong.

"If he has said somebody told him that, some credible source, then I believe that," the California Democrat told reporters after a campaign appearance at a retirement community.

She continued: "That's up to Gov. Romney to release his returns" and disprove the rumors.

So far, Romney only has released his 2010 tax return. He has promised to release his 2011 return after it's completed later this year.

At the White House, press secretary Jay Carney deflected repeated questions about Reid's allegations by referring reporters to Reid's office and stressing the "tradition" of presidential candidates releasing multiple years of tax returns.